UPDATE Thursday, Dec. 7, 2017

Former Gov. Phil Bredesen officially launched his bid for U.S. Senate Thursday, announcing his run with an online video.

In the more than two minute video, Bredesen sits on a chair on a porch while discussing a host of issues facing the country, including gridlock in Washington, D.C., the opioid crisis and the need to fix the Affordable Care Act.

"I'm running for the Senate because I have the right kind of experience and the actual track record that it will take to start working across party lines to fix the mess in Washington and bring common sense back to our government," Bredesen said.

The former governor — a political moderate and fiscal conservative who recently turned 74 — was the last Democrat to win a statewide election in Tennessee. He won all 95 counties in 2006 en route to his re-election as governor.

Although Tennessee's political landscape has drastically shifted since then — Republicans control both U.S. Senate seats, seven of nine Congressional seats, the governor's mansion and super majorities in both state legislative chambers — Bredesen's candidacy is widely seen as a game-changer, perhaps turning Tennessee into a battleground.

Also seeking the Democratic nomination is James Mackler, an Iraq War veteran and Nashville attorney. Chattanooga Mayor Andy Berke has previously expressed interest in the entering the race but may be reticent to do so with Bredesen's candidacy.

On the Republican side, U.S. Rep. Marsha Blackburn, former U.S. Rep. Stephen Fincher and Dr. Rolando Toyos are seeking the GOP nomination.

Phil Bredesen

Age: 74

Hometown: longtime Nashville resident (originally from New Jersey)

Occupation: Businessman

Family: Wife, one child

ORIGINAL STORY Wednesday, Dec. 6, 2017

Former Tennessee Gov. Phil Bredesen is set to officially enter the race for U.S. Senate, setting up a blockbuster election for the seat to be vacated by Sen. Bob Corker.

Three sources confirmed the Democrat's candidacy, as first reported by the Nashville Post, on Wednesday.

Bredesen is expected to formally announce his candidacy Thursday morning.

The former governor, who recently turned 74 years old, was the last Democrat to win statewide election. He won all 95 counties in 2006 en route to his re-election as governor.

Tennessee Governor Phil Bredesen speaks about Singer & Songwriter Dolly Parton during her induction into the Music City Walk of Fame, At Hall of Fame Park on Nov. 8, 2009, in Nashville, Tennessee. Photo by Rick Diamond/Getty Images

Although Tennessee's political landscape has drastically shifted since then, with Republicans controlling both U.S. Senate seats, seven of nine Congressional seats, the governor's mansion and supermajorities in both state legislative chambers, Bredesen candidacy makes the race immediately competitive for Democrats.

In October, political analyst Charlie Cook of The Cook Political report said Tennessee’s Senate race would become a toss-up if Bredesen runs and that the seat would likely remain Republican if he did not.

It is unclear what impact the former governor's candidacy will have on Democrat James Mackler, an Iraq War veteran and Nashville attorney, is also seeking the nomination. Chattanooga mayor Andy Berke has expressed interest in the Democratic nomination as well.

On the Republican side, U.S. Rep. Marsha Blackburn, former Congressman Stephen Fincher and Dr. Rolando Toyos are seeking the nomination.